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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Standard File Control Opcodes</h2><blockquote><pre>#define SQLITE_FCNTL_LOCKSTATE        1
#define SQLITE_GET_LOCKPROXYFILE      2
#define SQLITE_SET_LOCKPROXYFILE      3
#define SQLITE_LAST_ERRNO             4
#define SQLITE_FCNTL_SIZE_HINT        5
#define SQLITE_FCNTL_CHUNK_SIZE       6
#define SQLITE_FCNTL_FILE_POINTER     7
#define SQLITE_FCNTL_SYNC_OMITTED     8
</pre></blockquote><p>
These integer constants are opcodes for the xFileControl method
of the <a href="../c3ref/io_methods.html">sqlite3_io_methods</a> object and for the <a href="../c3ref/file_control.html">sqlite3_file_control()</a>
interface.</p>

<p>The <a href="../c3ref/c_fcntl_chunk_size.html">SQLITE_FCNTL_LOCKSTATE</a> opcode is used for debugging.  This
opcode causes the xFileControl method to write the current state of
the lock (one of <a href="../c3ref/c_lock_exclusive.html">SQLITE_LOCK_NONE</a>, <a href="../c3ref/c_lock_exclusive.html">SQLITE_LOCK_SHARED</a>,
<a href="../c3ref/c_lock_exclusive.html">SQLITE_LOCK_RESERVED</a>, <a href="../c3ref/c_lock_exclusive.html">SQLITE_LOCK_PENDING</a>, or <a href="../c3ref/c_lock_exclusive.html">SQLITE_LOCK_EXCLUSIVE</a>)
into an integer that the pArg argument points to. This capability
is used during testing and only needs to be supported when SQLITE_TEST
is defined.</p>

<p>The <a href="../c3ref/c_fcntl_chunk_size.html">SQLITE_FCNTL_SIZE_HINT</a> opcode is used by SQLite to give the VFS
layer a hint of how large the database file will grow to be during the
current transaction.  This hint is not guaranteed to be accurate but it
is often close.  The underlying VFS might choose to preallocate database
file space based on this hint in order to help writes to the database
file run faster.</p>

<p>The <a href="../c3ref/c_fcntl_chunk_size.html">SQLITE_FCNTL_CHUNK_SIZE</a> opcode is used to request that the VFS
extends and truncates the database file in chunks of a size specified
by the user. The fourth argument to <a href="../c3ref/file_control.html">sqlite3_file_control()</a> should
point to an integer (type int) containing the new chunk-size to use
for the nominated database. Allocating database file space in large
chunks (say 1MB at a time), may reduce file-system fragmentation and
improve performance on some systems.</p>

<p>The <a href="../c3ref/c_fcntl_chunk_size.html">SQLITE_FCNTL_FILE_POINTER</a> opcode is used to obtain a pointer
to the <a href="../c3ref/file.html">sqlite3_file</a> object associated with a particular database
connection.  See the <a href="../c3ref/file_control.html">sqlite3_file_control()</a> documentation for
additional information.</p>

<p>The <a href="../c3ref/c_fcntl_chunk_size.html">SQLITE_FCNTL_SYNC_OMITTED</a> opcode is generated internally by
SQLite and sent to all VFSes in place of a call to the xSync method
when the database connection has <a href="../pragma.html#pragma_synchronous">PRAGMA synchronous</a> set to OFF.
Some specialized VFSes need this signal in order to operate correctly
when <a href="../pragma.html#pragma_synchronous">PRAGMA synchronous=OFF</a> is set, but most
VFSes do not need this signal and should silently ignore this opcode.
Applications should not call <a href="../c3ref/file_control.html">sqlite3_file_control()</a> with this
opcode as doing so may disrupt the operation of the specialized VFSes
that do require it.
</p><p>See also lists of
  <a href="objlist.html">Objects</a>,
  <a href="constlist.html">Constants</a>, and
  <a href="funclist.html">Functions</a>.</p>
